Skip to main content
Information Security

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

17
  • those are not likely to be the open ports on your router, but ports made accessible by your ISP to their own resources - simple test: browse to your IP and connect to FTP Commented Aug 31, 2017 at 23:46
  • That is correct, these ports are ports that ISPs usually intercept to either protect the average user from accidentally opening these ports and getting hacked, and/or because their terms of service don't allow running FTP and HTTPD servers. Try to access those services and see what you get. Commented Sep 1, 2017 at 13:00
  • @ThomasCarlisle thank you. Still, why is my ISP advertising these ports as open to the outside world, does it not make more sense that these ports are filtered? Commented Sep 1, 2017 at 19:43
  • @schroeder thank you. If I run ftp nn.nnn.nnn.nnn from the command line, from outside of my LAN, it shows as "Connected to nn.nnn.nnn.nnn.". Does this mean that anyone, who knew my external IP Address, could create a connection in this manner? For what purpose would my ISP want this configuration, does it not create a security flaw? Commented Sep 1, 2017 at 20:10
  • 1
    @ThomasCarlisle I also powered off my home router, and got exactly the same results when running nmap and ftp nn.nnn.nnn.nnn.. So I can see now that these open ports are not directly related to my home router. This raises more questions for me than it answers however. How does my ISP forward packets to me? Using the same IP address? But that IP address is not actually my address. Perhaps it's more to do with the MAC address of my home router. Does my ISP translate addresses. Why does my ISP advertise these ports as open on its systems. I clearly have a lot of work to do. Thanks again. Commented Sep 3, 2017 at 12:59